This invention relates generally to a process for extraction of seeds and specifically to a process for the preparation of useful materials such as dietary fiber, oleoresin and fixed oils from the seeds of Fenugreek (Trigonella Foenum Graecum L). This invention also relates to an extraction apparatus for extraction of the seeds.
Fenugreek is an herbaceous plant of the leguminous family and is native to Western Asia, from where it has spread widely over Europe, the Mediterranean and rest of Asia. It is one of the oldest cultivated plants and through the ages has found wide application as a food, a food additive and in the traditional medicine of every region in which it has been cultivated. For example, one of its earliest uses was in Egypt where it was used as a flavoring agent in bread and other foods and as an anti-pyretic. Similarly, in India and elsewhere, the leaves, and both the ripe and unripe seeds of Fenugreek are used as vegetables and the ripe seed further, has numerous applications in the traditional medicine system of India. The seeds also function as a preservative and are added to pickles, chutneys and other similar products. In modem food practice, the seeds or the extract are used in bakery products, frozen dairy products, meat products, relish, condiments, candy, gravy sauces, gelatin puddings and in alcoholic and non-alcoholic beverages. The leaves of Fenugreek are also used in forage for cattle and the seeds as an additive in cattle feeds. Because of its significant nutrition potential, the seeds and products made therefrom are also used as food supplements.
Fenugreek has been used in treating colic flatulence, dysentery, diarrhea, dyspepsia with loss of appetite, chronic cough, dropsy, enlargement of liver and spleen, rickets, gout and diabetes. The seed is stated to be a tonic. It is also used in post-natal cure and to increase lactation in nursing mothers. Its lactation inducing property is also used with milch cattle to increase the yield of milk. The seed was used as a cure for baldness in the middle ages and today it is used as part of hair tonics in some countries. The seed also has several applications in veterinary medicine.
Modem medicine is beginning to provide confirmation of many of the traditional medicinal applications of Fenugreek. For example, it has been established that the saponins of Fenugreek and also the galactomannans contained in the mucilage of fenugreek have a beneficial effect on glucose, insulin and cholesterol metabolism.
Thus, these components along with the dietary fiber contained in fenugreek have an important role in the treatment and management of several disorders such as obesity, coronary heart disease, diabetes, piles, fissures, chronic constipation and diverticulitis. Similarly, the fixed oils of fenugreek are reported to contain the principle that causes increased lactation. The saponins mentioned above are also reported to contain active components that are anti-carcinogenic, anti-microbial and/or anti-oxidant. The saponins further contain a compound, a sapogenin called diosgeninxe2x80x94estrogen, that is the precursor in the manufacture of sexual hormones and oral contraceptives.
Fenugreek seed contains a large number of individual compounds such as volatile oil, fixed oils, proteins, carbohydrates, resins, pigments, vitamins, minerals and others. Typical analyses of fenugreek seed are shown in the tables below.
The essential oil is conventionally obtained by steam distillation of the dried seed. Steam distillation does not extract the taste factors of Fenugreek as these are fairly non-volatile resinous compounds. Thus, when incorporated in foods, the essential oil isolated by prior art methods merely provides the odor of fenugreek and not the pungent taste of Fenugreek.
The oleoresin has been obtained by extraction with an organic solvent. However, in the conventional processes, traces of the solvent remain and tend to interfere with the aroma and taste of the oleoresin. Further, conventional processes employ solvents such as chlorinated solvents, e.g, ethylene dichloride and methylene dichloride, which are toxic and pose health threats. Chlorinated solvents potentially undergo decomposition when heated to form hydrogen chloride and carbonyl chloride, which by-products are toxic. Food regulations of most countries, however, dictate that these even trace amounts of these toxic solvents be removed. Removal of the solvent traces is extremely difficult. Removal is often effected by evaporation of the solvent traces under heat and/or vacuum. However, this invariably results in a degree of damage to the heat labile flavor components and the consequent change of the oleoresins"" flavor. Other methods of removing the solvent have been developed; however, all those methods are costly, cumbersome and not always fully successfiil. The conventional production of oleoresin that is substantially true to the aroma and taste of the seed is an extremely difficult operation requiring skill and care at each stage of processing. Moreover, conventional processes are extremely unreliable due to significant variability in the quality of the isolated oleoresin.
The bitterness present in conventional extracts of Fenugreek typically comes from the hydrolytic breakdown of lipids present in the fixed oil fraction. This problem exists predominantly in conventional processes that employ steam or water extraction of components from Fenugreek seeds. The hydrolysis of lipids, which occurs over a period of time leads to rancidity and imparts a dark brown to black color to the seed. Therefore, the bitterness and darkened coloration is passed on to the residual dietary fiber of fenugreek even after the extraction. A dietary fiber product having such bitterness and coloration is not acceptable as a food product, supplement or additive.
Because of its inertness, the importance of dietary fiber was not realized until the link between fiber deficiency and several disorders and diseases was conclusively established. Modern diets, particularly the urban ones, include a large amount of processed foods that are carbohydrate rich and fiber deficient. Fiber deficiency is now known to be the causative factor of several disorders, such as heart ailments and coronary artery disease, diabetes, constipation, colon cancer, piles, fissures, gallstones and others. A diet having adequate amount of dietary fiber is now known to be important not only from the point of view of preventing the disorders but also in the cure and management thereof. Public health and Nutrition bodies now prescribe a minimum daily dietary fiber intake and the recommended figures range between 30 to 40 gm per day per person. For individuals having fiber related disorders, dietary fiber offers either a cure or help in the management thereof. It has been reported that high sugar and fat rich foods, i.e., fiber depleted foods, form 55 to 60% of the daily calorie intake in many countries as compared to 15-20% a century ago.
Insoluble dietary fiber mainly comprises cellulose, lignins and some hemicelluloses; while, soluble dietary fiber mainly comprises pectin, gums and some hemicelluloses. The two types play somewhat different roles in the intestinal tract. The former enhances the food bulk and generates a feeling of satiety although the feeling is not as strongly perceived as in the case of the latter. Increased satiety leads to lower food intake. Insoluble fiber also causes increase in faecal bulk by virtue of its indigestible nature and because of fermentation thereof, in the intestine. The insoluble fiber causes quicker movement of the food mass along the intestinal tract. Soluble fiber on the other hand, tends to enhance the viscosity of the food mass in the intestinal tract and slows down the transit down the tract thereof. The feeling of satiety is also observed with diets incorporating soluble fibers and as mentioned the feeling is stronger than for insoluble fibers. The food intake therefore, tends to go down also with soluble fibers. Soluble fiber also undergoes fermentation in the gut producing some volatile fatty acids which are important from the point of view of nutrition. These fatty acids are absorbed by the intestine.
Soluble fiber of Fenugreek, guar gum, oat bran, oat gum, oat hulls, bengal gram and pectin have a strong cholesterol lowering effect. Similar lowering has also been observed in the case of serum triglycerides/triacylglycerols. HDL and LDL cholesterol are also favorably affected and an improvement of the HDL/LDL ratio is observed with soluble fiber. The beneficial effect also extends to liver cholesterol and triglycerides.
The groups of above compounds that are of significance commercially (and industrially) include essential oil, fixed oils, oleoresin and dietary fiber. These are generally obtained by fractionation of Fenugreek using one or more processes such as steam distillation, hydro-extraction, solvent extraction, hydrolysis and others. These conventional processes, however, generally do not provide acceptable products or are limited to providing only one useful product obtained from Fenugreek.
One extraction process requires that the solid material be charged into a vessel (tank) and fresh extraction solvent added thereto. Enough solvent is added, i.e., generally up to a level of few centimeters above the solids level, to ensure complete submergence of the solid material. Such an extraction system is referred to herein as a static system and the solid material being extracted as a xe2x80x9cbed of solidsxe2x80x9d or xe2x80x9csolid bedxe2x80x9d. Where extraction is required to be conducted at a temperature above ambient, the vessel is optionally provided with a jacket for circulation of a heating medium such as steam, hot water or others. At the end of extraction, the extract and the extracted solids are removed from the vessel. The extraction solvent is drained from the vessel either intermittently or continuously by way of a false bottom comprising a perforated plate and/or a filtration medium. The chief drawback of a conventional static system that employs the addition of unheated fresh solvent is the difficulty of maintaining a uniform temperature in the bed particularly when heat is added, by heating coils, into the vessel contents. The temperature is found to be neither uniform throughout the bed nor over the period of extraction. Such nonuniformities in temperature and solvent concentration render the extraction process somewhat non-reproducible in that small but subtle differences in the composition and quality of the extract are observed from batch to batch. For example, in conventional static extraction process, the moisture content present in the seed passes into the extraction solvent at the commencement of the extraction. Thus, during the rest of the extraction, the solvent in contact with the seeds is somewhat diluted by that moisture resulting in a lower driving force for extraction.
When fresh, i.e., solute-free, solvent is contacted with solids to be extracted the driving force for extraction (for dissolution of solute in solvent) is high. However, the driving force continually diminishes as extraction proceeds. Actually, a point is reached where the rate of extraction is so diminished that further extraction is uneconomical. Generally, the extract is then drained out and a new batch of solvent added to the bed to continue the extraction. The new batch of solvent may be either fresh (solute free) solvent or a dilute extract from another extraction batch, e.g., countercurrent extraction method. In another embodiment of the static system the solvent containing extracted solute is continuously circulated to improve contact of the solvent and solids; however, this reduces extraction efficiency due to the extraction solvent already containing solute.
Conventional static systems have the same drawback of nonuniformities. In a static system with the continuous solvent re-circulation, channeling of the solvent in the bed also causes the nonuniformities. A further disadvantage is that a continuous circulation system requires a larger amount of solvent, which adds to the costs of solvent recovery by evaporation or other means. Also, a solvent re-circulation system that recycles used solvent requires additional capital equipment in the form of additional solvent pumps, tanks and other items. Another drawback of conventional static systems is that the contact between the solvent and solid is not efficient. Thus even if the driving force is high, for example as at commencement of extraction, the actual rate of solute dissolution remains low.
One approach to the problem of low dissolution rates in the prior art is to employ a stirred/agitated tank reactor in which the solvent and solid are contacted. Such a system is referred to herein as a dynamic system. A dynamic system can be adapted to the continuous or intermittent solvent re-circulation and also to the counter current arrangement. A dynamic system undoubtedly provides better solventxe2x80x94solid contact but has the drawback of a greater capital investment. Also, it requires a larger amount of solvent leading to increased capital costs and increased operating costs in solvent evaporation or removal and recovery.
Processes for the extraction of Fenugreek are disclosed in U.S. Pat. No. 5,658,571 to Gopalan et al., U.S. Pat. No. 5,997,877 to Chang, U.S. Pat. No. 6,013,289 to Blank et al., and U.S. Pat. No. 6,013,304 to Todd. However, none of these references disclose the presently claimed extraction process and associated process equipment.
The process of Gopalan et al. is a static type process and consequently suffers from the drawback of the nonuniformities discussed above. Gopalan et al. disclose the use of a single solvent that apparently extracts a mixture of fenugreek fractions. Gopalan et al. do not disclose recovery of the individual Fenugreek fractions by selective sequential solvent extraction with different solvents. Gopalan et al. also disclose that the extraction solvent is heated after the Fenugreek seed is immersed in the solvent. Moreover, most of the solvents used by Gopalan et al., with the exception of ethanol and isopropanol, are either chlorinated or toxic or both, and therefore somewhat unsuitable for applications involving food grade products. Gopalan et al. also disclose multiple extractions, each with a separate batch of fresh solvent or each with solvent containing extracted solutes. In neither embodiment do Gopalan et al. add a heated solvent to the Fenugreek seeds. In addition, Gopalan et al. do not disclose repeatedly contacting the Fenugreek seeds with freshly distilled hot recirculated solvent obtained from a reservoir containing the extraction solvent comprising solute.
The process of Chang is a dynamic type process, which also suffers from the associated disadvantage/drawbacks outlined above. The Chang process produces oleoresin wherein the fixed oils therein have not been removed. Therefore, the oleoresin product is susceptible to bitterization and discoloration caused by rancidity in the fixed oils. The Chang process introduces water into the system by tempering the seeds prior to extraction and by the use of 95% ethanol in the extraction process even before the removal of the bulk of fixed oils therein.
Accordingly, the known processes for extracting components from Fenugreek provide unacceptable products in terms of excessive colorization, bitterness, and rancidity. None of the known art discloses a process for separating fixed oil and then oleoresin from Fenugreek seeds to obtain a dietary fiber rich meal.
The present invention addresses the problems and drawbacks associated with conventional processes for obtaining useful products from Fenugreek seeds. In particular, low boiling non-toxic solvents have been selected where the removal of trace amounts of solvent from the useful products is comparatively easy. One of the highlights of the process of the invention is that the process of extraction of oleoresin, although highly simple and economical, reproducibly provides a high purity food grade product oleoresin by minimizing contact temperature nonuniformities inherent in conventional processes. By continuously providing freshly distilled recycled hot solvent, the present process is cost effective, provides maximum extraction efficiency, and balances the contact ratio and contact time to provide an overall economical process in terms of operating and capital costs. Contact of seeds with water during extraction is eliminated by avoiding contact of the seeds with water at least until the bulk of the fixed oils have been extracted out of the seeds by the first extraction solvent. The process of the invention can be used to provide a dietary fiber having a fat content of less than about 0.5% or less than about 0.3%.
The process of the invention employs a 2-stage extraction process in which two separate solvents are used, the pair of solvents being selected such that the first solvent extracts the fixed oils exclusively, or almost exclusively, and the second solvent extracts the oleoresin and optionally other components present in the Fenugreek seeds. The second solvent extracts out substantially all of the remaining fixed oils in the seed, thereby reducing the lipid content remaining in the residual dietary fiber generally to below 0.5%, below 0.3%, or below 0.1%.
A key feature of the present invention is that the fixed oils of the seed are isolated and removed as a first step so as to ensure a dietary fiber having little to no bitterness or discoloration. The second fraction obtained by solvent extraction of the seed from which the fixed oils have been removed is quite faithful to the aroma and taste of fenugreek. The second fraction therefore referred to herein and in the art as the oleoresin, despite the fixed oils having been separated therefrom. By removing a major portion of the fixed oils from the seeds with the first extraction solvent, the present process eliminates or reduces the occurrence of bitterness and excessive coloration of products obtained by subsequent processing of the seeds.
This invention provides a process for the isolation of essential oil, oleoresin, fixed oil, proteins, vitamins minerals, saponins, and/or sapogenins from Fenugreek seeds. These products are obtained by fractional separation of some of these fractions of Fenugreek seed. The invention provides a process for the production of substantially pure food grade dietary fiber, oleoresin and fixed oils from Fenugreek seeds.
The process of the invention comprises the following general features: 1) a two-stage process employing two different solvents having solubility characterisitics such that the first solvent selectively extracts out the bulk of its fixed oil fraction of the seeds during the first stage and the second solvent is effective in extracting out substantially all of the oleoresin fraction and substantially all of the small amount of fixed oils remaining in the first extracted mass; 2) contact of solids with freshly condensed solvent in both stages such that the bed is substantially continuously charged with the freshly condensed solute-free solvent thereby maximizing extraction efficiency; 3) draining of the solvent in contact with the bed of seeds each time the bed is completely submerged by the solvent such that the bed is substantially continuously in contact with freshly condensed solute free solvent and the extraction rate is maximized throughout the extraction, the contact being substantially at the highest feasible temperature, which is generally the condensing temperature of the solvent; 4) addition of hot freshly condensed solvent to the bed of seeds such that the process conserves heat, is simplified and requires very simplified extractor equipment; 5) evaporation of the extraction solvent from the first extract yields a substantially pure fixed oil fraction generally requiring no further separation and purification; 6) evaporation of the extraction solvents from the extracted fractions is not an added cost as the process is based on continuous evaporation and condensation of solvents; 7) the pair of extraction solvents employed in the process are low-boiling, non-toxic and non-hazardous from health point of view and traces thereof are easy to remove/recover; and 8) the extraction of the major portion (generally at least about 85%) of the fixed oils fraction during the first extraction stage thereby allowing the use of even aqueous alcohol solvents during the second extraction stage while minimizing the risk of bitterisation and discoloration (excessive coloration), the advantage of use of the aqueous alcohol solvents during the second extraction stage being that it rapidly and effectively extracts out the oleoresin and the remainder of fixed oils from the seeds; 9) a simple, novel, cost-effective procedure for separation of the oleoresin and fixed oils from the second extract; and 10) potential for the use of solvent mixtures.
According to one aspect of the invention there is provided a process for the extraction of Fenugreek (Trigonella Foenum Graecum L.) seeds to produce substantially pure dietary fiber, oleoresin and fixed oils comprising the steps of:
1) optionally, sorting and cleaning Fenugreek seeds and crushing, grinding, flaking and/or milling thereof;
2) extracting the seeds with a hot substantially freshly condensed first solvent (or mixture of solvents) in a first stage of extraction to yield a first extract and partly extracted seeds;
3) extracting the partly extracted seeds with a hot substantially freshly condensed second solvent (or mixture of solvents) in a second stage of extraction to yield a second extract and a wet dietary fiber; and
4) drying of the wet dietary fiber to form a substantially pure dietary fiber.
The process of the invention can also include one or more of the following steps:
heating the first extract to evaporate the first solvent therefrom to yield substantially pure fixed oils;
heating the second extract to evaporate the second solvent therefrom to yield a product mixture of oleoresin and fixed oils;
treating the product mixture with ethanol for a period of time and at a controlled temperature to form a treated mixture;
cooling the treated mixture to yield a liquid comprising a heavy phase and a light phase;
separating the heavy and light phases, wherein the heavy phase comprises the substantially pure oleoresin;
separating, by filtering or other means, any solids or crystallized impurities, such as fats and waxes, from the light phase; and
evaporating ethanol from the light phase to yield the substantially pure fixed oils.
The invention also provides a method of obtaining valuable components from Fenugreek seeds comprising the steps of:
extracting the Fenugreek seeds with a first extraction solvent to provide a first useful extract and a first extracted mass;
extracting the first extracted mass with a different second extraction solvent to provide a second useful extract and a second extracted mass; and
removing solvent from the second extracted mass to provide a useful solid.
Specific embodiments of this aspect of the invention include those wherein: 1) the first extraction solvent is petroleum ether and the second extraction solvent is 90-5% ethanol (aq.); 2) the first useful extract comprises fixed oils and the second useful extract comprises oleoresin; 3) the first solvent is selected from the group consisting of petroleum ether, hexane, n-propanol, isopropanol, and a combination thereof; 4) the second solvent is selected from the group consisting of ethanol, isopropanol, aqueous isopropanol, aqueous ethanol and a combination thereof; 5) a major portion of the first extraction solvent is removed from the first useful extract to form substantially pure fixed oil; 6) a major portion of the second extraction solvent is removed from the second useful extract to form a mixture comprising oleoresin and optionally fixed oil; 7) the mixture of oleoresin and fixed oil is treated with an ethanolic solution to form substantially pure oleoresin and a mixture of other components including fixed oil; 8) solids are removed from the mixture of other components and fixed oil and the ethanol and water are evaporated to form substantially pure fixed oil; 9) the useful solid comprises a dietary fiber; and/or 10) the seeds are cleaned, ground, sorted, tempered, flaked, crushed and/or milled prior to extraction.
According to other aspects of the invention, there is provided a dietary fiber, fixed oil or oleoresin of fenugreek seed produced by the process of the invention optionally conducted in the extraction system of the invention.
Accordingly, the invention also provides a substantially pure fixed oil obtained from Fenugreek seeds by a process comprising the steps of:
substantially continuously contacting a freshly condensed hot first extraction solvent with a bed of Fenugreek seeds for a period of time and at a constant temperature sufficient to form an extract comprising fixed oil and the first extraction solvent, wherein the freshly condensed first extraction solvent is obtained from a reservoir containing the extract;
separating the Fenugreek seeds from the extract; and
removing at least a major portion of the extraction solvent from the extract to form the fixed oil.
Specific embodiments of the invention include those wherein: 1) the first extraction solvent is selected from the group consisting of petroleum ether, hexane, n-propanol, isopropanol, and a combination thereof; 2) the temperature of the extraction solvent approximates the boiling point or the condensation temperature of the first extraction solvent; 3) wherein the fixed oil comprises fatty acid esters such as the glycerol esters of palmitic, arachidic acid, behenic, oleic, linoleic and/or linolenic acid; 4) the ratio of the Fenugreek seeds to the first extraction solvent from about 1:1 to 1:5 weight/volume (kg/L).
The invention also provides a substantially pure oleoresin obtained from Fenugreek seeds by a process comprising the steps of:
contacting Fenugreek seeds with a first extraction solvent for a period of time and at a temperature sufficient to form a first extract comprising fixed oil and the first extraction solvent, wherein a major portion of fixed oil present in the Fenugreek seed is removed by the first extraction solvent;
separating the Fenugreek seeds from the first extract to form partially extracted seeds;
contacting the partially extracted seeds with a different second extraction solvent for a period of time and at a temperature sufficient to form extracted seeds and a second extract comprising oleoresin, fixed oil and the second extraction solvent;
separating the extracted seeds from the second extract;
removing at least a major portion of the second extraction solvent from the second extract to form a concentrate;
contacting the concentrate with an ethanolic solution to form a heterogeneous solution comprising an oleoresin-containing layer and one or more other layers; and
isolating the oleoresin-containing layer to form a substantially pure oleoresin.
Specific embodiments of this aspect of the invention include those wherein: 1) the Fenugreek seeds are contacted with the first extraction solvent continuously, semi-continuously or batchwise; 2) the first and/or second extraction solvents are percolated through the Fenugreek seeds; 3) the first and/or second extraction solvents are freshly distilled; 4) the first extraction solvent is obtained from a reservoir comprising fixed oil and the first extraction solvent; 5) the second extraction solvent is obtained from a reservoir comprising oleoresin, second extraction solvent and optionally fixed oil; and/or 6) the ethanolic solution comprises ethanol or ethanol and water.
The invention further provides a dietary fiber obtained after extraction of Fenugreek seeds by an extraction process comprising the steps of:
extracting the Fenugreek seeds with a first extraction solvent to remove fixed oil from the seeds;
extracting the partly extracted seeds with a different second extraction solvent to remove oleoresin from the seeds; and
separating the seeds from any remaining extraction solvent to form a dietary fiber.
Specific embodiments of this aspect of the invention include those wherein: 1) the solvent temperature approximates the boiling point or the condensation temperature of the respective extraction solvent; 2) the first and second solvents are hot and freshly condensed when used to extract the Fenugreek seeds; 3) at least a major portion of fixed oils are removed from the dietary fiber by extraction; 4) wherein at least a major portion of oleoresin are removed from the dietary fiber by extraction: 5) the dietary fiber has little to no taste, is light yellow to light brown, and has little to no odor; 6) the dietary fiber has a fat content of less than 0.5%, less than 0.3% or less than 0.1%; and/or 7) the dietary comprises approximately equal amounts of soluble fiber and insoluble fiber.
The invention thus provides a method or process for making substantially pure food grade dietary fiber from fenugreek seeds and to recover two other fractions thereof, namely, oleoresin and fixed oils also in substantially pure form and of food grade quality. The invention also provides substantially pure food grade dietary fiber, oleoresin and fixed oils, wherein de-bitterisation of the dietary fiber is also achieved.
According to another aspect of the invention, there is provided an extraction system for the extraction of fenugreek seeds comprising:
an extraction vessel having means for holding the bed of solid materials to be extracted;
a reboiler;
a condenser; and
conduits interconnecting the condenser and the reboiler so as to conduct vaporized solvent from the reboiler to the condenser.
The condenser effects condensation of the solvent vapors to form a freshly distilled hot solvent that is contacted with the bed at substantially the condensing temperature thereof. The system also comprises means for periodically draining the extracts from the reboiler, means for controlling heat input to the reboiler, cooling means in the condenser, and other control means as needed.
Other aspects of the invention provide finished products comprising the above-described fixed oil, oleoresin or dietary fiber. Some embodiments of this aspect include: 1) omega fatty acids derived from the fixed oils of fenugreek; 2) essential oil of fenugreek; 3) resinous taste compound(s); 4) flavoring compound(s); 5) galactomannans; 6) protein; 7) amino acids such as lysine; 8) insoluble fiber; 9) soluble fiber; 10) vitamin(s); 11) mineral(s), such as sodium, potassium, iron and phosphorous; 12) choline; and/or 13) carbohydrates. These products can be used in vitamin supplements, nutritional supplements, dietary supplements, and/or as food additives.
Thus, the invention provides a fenugreek-based dietary fiber that can be consumed as a supplement or added to other food during the process of cooking thereof. In addition, other nutrients may be added to the dietary fiber of the invention to provide a greater nutritional balance and/or to restore nutritional deficiencies. A dietary fiber product may also comprise added taste, flavor and/or coloring agents.